VERNON — When Det. Michael Morrissey interviewed Richard Lapointe about the rape and murder of an 88-year-old woman in 1987, he was either determined to get a confession from the mentally disabled man whom he believed was guilty or he remained open-minded and was merely seeking the truth. LaPointe’s lawyer and a prosecutor tried to settle that question in court on Tuesday.

“The investigation had focused on him as a prime suspect, but I hadn’t drawn that conclusion,” Morrissey, now retired, testified in Superior Court in Rockville during Lapointe’s third and, likely last, bid for a new trial.

Lapointe was convicted in 1992 of raping and killing Bernice Martin, his then-wife’s grandmother, and setting her apartment in Manchester on fire. He was interviewed by police on July 4, 1989.

During direct examination on Tuesday, Lapointe’s attorney, Paul Casteleiro, suggested that in his quest for a confession, Morrissey overlooked inconsistencies in Lapointe’s admission to Morrissey and failed to ask important questions.

In his confession, Lapointe said he had strangled 88-year-old Bernice Martin with his hands, but the medical examiner determined she had been strangled with a ligature. Lapointe also said he stabbed Martin on the couch, but forensic evidence suggested the stabbing occurred on the victim’s bed.

“Don’t you want to wrap up those inconsistencies when you’re trying to wrap up a murder investigation?” Casteleiro asked.

Karen Martin, Lapointe’s ex-wife, had told Morrissey that Lapointe had left to walk the dog for about 20 minutes before the family had dinner at 5 p.m. on the night her grandmother was killed. But Morrissey, while interviewing Lapointe, did not ask how much time he spent at the victim’s home while committing the crime, Casteleiro pointed out.

During cross-examination, state prosecutor Michael O’Hare discussed with Morrissey the evidence that led investigators to Lapointe. Tests on a semen stain found at Martin’s apartment showed that it contained no sperm and had come from a person with Type A blood.

Lapointe has Type A blood and had had a vasectomy, which could explain the absence of sperm in the semen.

“All those things pointed to [Lapointe]?” O’Hare asked.

“Yes,” Morrissey replied.

Lapointe also gave details about how the semen stain got on the bedding, saying that he’d masturbated, according to Morrissey’s testimony.

“All these things corroborated the truthfulness of Richard Lapointe’s statement to you?”

“Yes.”

Inaccuracies in confessions are not rare, Morrissey also testified. Sometimes offenders provide inaccurate details to minimize the offense they committed or because they’re deliberately misleading investigators, he said.